Thursday, September 6, 2012

Multiple Events Caused K-Pg Mass Extinction?

Although abundant evidence now exists for a massive bolide impact coincident with the Cretaceous–Paleogene (K–Pg) mass extinction event (~ 65.5 Ma), the relative importance of this impact as an extinction mechanism is still the subject of debate. On Seymour Island, Antarctic Peninsula, the López de Bertodano Formation yields one of the most expanded K–Pg boundary sections known. Using a new chronology from magnetostratigraphy, and isotopic data from carbonate-secreting macrofauna, we present a high-resolution, high-latitude paleotemperature record spanning this time interval. We find two prominent warming events synchronous with the three main phases of Deccan Traps flood volcanism, and the onset of the second is contemporaneous with a local extinction that pre-dates the bolide impact. What has been termed the K–Pg extinction is potentially the sum of multiple, independent events, at least at high latitudes.

So, was the Chicxulub meteorite impact before the peak Deccan volcanism as Keller and colleagues say or was it 200,000- 300,000 thousand years after Deccan volcanism as this new paper by Tobin et. al. suggests. The famous iridium anomaly observed in many K-Pg boundary sections has been dated to after the main phase of Deccan volcanism indicating that there was a meteorite impact some time after peak volcanism.

Or were there two impacts with the Deccan volcanism sandwiched in between? It does seem that the single bullet theory for the K-Pg mass extinction is under serious threat.

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ABOUT THIS BLOG

I am a Sedimentary Geologist. On Rapid Uplift I write mostly about topics within the geosciences, but sometimes on biological evolution and environmental issues. I like to travel and in my free time I teach 12 year old kids soccer and rugby.